Optimal Channel Adaptation of Scalable Video Over a Multicarrier-Based Multicell Environment

To achieve seamless multimedia streaming services over wireless networks, it is important to overcome inter-cell interference (ICI), particularly in cell border regions. In this regard scalable video coding (SVC) has been actively studied due to its advantage of channel adaptation. We explore an optimal solution for maximizing the expected visual entropy over an orthogonal frequency division multiplexing (OFDM)-based broadband network from the perspective of cross-layer optimization. An optimization problem is parameterized by a set of source and channel parameters that are acquired along the user location over a multicell environment. A suboptimal solution is suggested using a greedy algorithm that allocates the radio resources to the scalable bitstreams as a function of their visual importance. The simulation results show that the greedy algorithm effectively resists ICI in the cell border region, while conventional nonscalable coding suffers severely because of ICI.     

Minimum Energy Transmission Over a Wireless Channel With Deadline and Power Constraints

We consider optimal rate-control for energy-efficient transmission of data, over a time-varying channel, with packet-deadline constraints. Specifically, the problem scenario consists of a wireless transmitter with $B$ units of data that must be transmitted by deadline $T$ over a fading channel. The transmitter can control the transmission rate over time and the required instantaneous power depends on the chosen rate and the present channel condition, with limits on short-term average power consumption. The objective is to obtain the optimal rate-control policy that minimizes the total energy expenditure while ensuring that the deadline constraint is met. Using a continuous-time stochastic control formulation and a Lagrangian duality approach, we explicitly obtain the optimal policy and show that it possesses a very simple and intuitive form. Finally, we present an illustrative simulation example comparing the energy costs of the optimal policy with the full power policy.      

Optimal Signaling Policies for Decentralized Multicontroller Stabilizability Over Communication Channels

In this note, we study the problem of distributed control over communication channels, where a number of distributed stations collaborate to stabilize a linear system. We quantify the rate requirements and obtain optimal signaling, coding and control schemes for decentralized stabilizability in such multicontroller systems. We show that in the absence of a centralized decoder at the plant, there is in general a rate loss in decentralized systems as compared to a centralized system. This result is in contrast with the absence of rate loss in the stabilization of multisensor systems. Furthermore, there is rate loss even if explicit channels are available between the stations. We obtain the minimum data rates needed in terms of the open-loop system matrix and the connectivity graph of the decentralized system, and obtain the optimal signaling policies. We also present constructions leading to stability. In addition, we show that if there are dedicated channels connecting the controllers, rate requirements become more lenient, and as a result strong connectivity is not required for decentralized stabilizability. We determine the minimum number of such external channels leading to a stable system, in case strong connectivity is absent.     

Optimal Channel Choice for Lossy Data Flow Transmission

We consider the optimal control problem for the load of several communication channels defined by independent Markov jump processes. Implicit information on the state of a channel is available in the form of a flow of losses whose intensity is proportional to the controllable load of this channel. The optimized functionals take into account the total throughput of channels and energy costs for data transmission over a fixed interval of time. We obtain optimal filtering equations for joint estimation of channel states. We construct a locally optimal strategy that explicitly depends on the set of state estimates.     

Optimal Transmission Rate Control Policies in a Wireless Link Under Partial State Information

We consider the problem of PHY layer transmission rate control for maximum throughput on a wireless link over a finite time horizon. For each link state there exists a most advantageous transmission rate for the controller. The controller needs to rely on incomplete link state information in the form of positive acknowledgements (ACKs) and negative acknowledgements (NACKs) for transmitted packets. We cast the problem as a partially observed Markov decision processes (POMDP). We focus on the special case of time-invariant or slowly time varying link quality with two states and two control options. In that case, the optimal control problem is a state estimation one and the optimal strategy is of threshold structure, where the thresholds are certain values of the belief of being in one of the two states. The policy admits a simple interpretation: increase rate when the number of successive ACKs exceeds a threshold, and decrease rate when the number of successive NACKs exceeds a threshold.      

最优证券组合的结构特征研究

在库恩－塔克条件基础上，研究了马尔科维茨理论框架内最优证券组合的结构特征，进－步扩展了关于最优证券组合结构特征和有效边界形状的现有成果。     

Optimal Maintenance Policies for a System With Multiechelon Risks

Aged fossil-fired power plants are on the great increase in Japan, and the importance of preventive maintenance (PM) increases for their steady operations. A plant consists of a wide variety of mechanical and electrical components. Various kinds of severe failures inherent in these components and their occurrence probabilities are different. A system fails when the total suffered damage exceeds a peculiar level, i.e., these components have their peculiar damage levels. The PM plan should be established, considering such levels of plant components. In this paper, kinds of peculiar cumulative damage levels are considered, and a system fails when the total damage exceeds these damage levels. The PM is performed when the total damage exceeds the managerial one . The expected cost per unit time between maintenances is secured, and the optimal managerial level which minimizes it is analytically discussed.     

Feedback Stabilization Over a First Order Moving Average Gaussian Noise Channel

Recent developments in information theory by Y.-H. Kim have established the feedback capacity of a first order moving average additive Gaussian noise channel. Separate developments in control theory have examined linear time invariant feedback control stabilization under signal to noise ratio (SNR) constraints, including colored noise channels. This note considers the particular case of a minimum phase plant with relative degree one and a single unstable pole at z=phi (with |phi| > 1) over a first order moving average Gaussian channel. SNR constrained stabilization in this case is possible precisely when the feedback capacity of the channel satisfies CFB ges log₂ |phi|. Furthermore, using the results of Kim we show that there exist linear encoding and decoding schemes that achieve stabilization within the SNR constraint precisely when CFB ges log₂ |phi|.     

瑞利信道中双门限检测算法性能仿真及研究

研究无线网络通信,提高信道性能,改进检测方法,感知频谱环境是认知无线电的首要任务,如何在衰落信道中提高频谱的检测性能对现有认知无线电技术提出挑战.采用瑞利信道为典型信道,针对不同的协作感知方法展开研究,确定将一种双门限感知法植入瑞利信道,克服了唯一门限较难确定及系统开销大的问题.通过仿真,结果表明,双门限法与传统检测方法相比,不仅提高了检测概率,且减小了不必要的系统开销.     

On a Model of Information Transmission through Unreliable Communication Channel

Consideration was given to the problems of error-free information transmission through an unreliable communication channel with allowance for duration of the arbitrarily distributed disturbing factor. It was assumed that the distribution functions of packet transmission time, inter-error duration, and time of elimination of the disturbing factor are arbitrary as well. The generalized probability of undistorted information transmission in a given time was obtained. The expectation of the time of error-free transmission was calculated, and its examination enabled determination of a rational strategy of information transmission.     

Transmission Rate Allocation in Multisensor Target Tracking Over a Shared Network

In a multisensor target tracking application running on a shared network, at what bit rates should the sensors send their measurements to the tracking fusion center? Clearly, the sensors cannot use arbitrary rates in a shared network, and a standard network rate control algorithm may not provide rates amenable to effective target tracking. For Kalman filter-based multisensor target tracking, we derive a utility function that captures the tracking quality of service as a function of the sensor bit rates. We incorporate this utility function into a network rate resource allocation framework, deriving a distributed rate control algorithm for a shared network that is suitable for current best effort packet networks, such as the Internet. In simulation studies, the new rate control algorithm engenders significantly better tracking performance than a standard rate control method, while the ordinary data transfer flows continue to effectively operate while using their standard rate control methods.      

基于流媒体的隐蔽通信可靠传输机制的研究

首先分析了原有流媒体隐蔽通信系统模型在传输机制上存在的问题.在此基础上改进了原有的传输方案,提出了一种新的基于流媒体的隐蔽通信的可靠传输机制,并进行实现和实际测试.实验结果表明,对于只有当载体满足一定条件时才可以嵌入的隐藏算法,新的传输机制也能保证可靠传输,性能较以前的方法也有长足的改善.     

Structural Properties,LQG Control and Scheduling of a Networked Control System with Bandwidth Limitations and Transmission Delays

The problem of simultaneous LQG control and scheduling of a Networked Control System (NCS) with constant network induced delays at input and output and bandwidth limitations is investigated. Delays are considered at plant as well as controller side. Sufficient conditions for controllability, stabilizability, reconstructibility and detectability of the underlying networked control system are drawn. The proposed conditions extend previous works on structural properties of NCS by capturing both plant and controller side delays together with bandwidth limitations. A framework for computing the optimal LQG controller for the NCS with a fixed scheduling is provided. The proposed modeling approach facilitates use of LQG as well as other control methods for NCSs with delays and bandwidth limitations. In order to optimize performance, a semi-online scheduling procedure is proposed based on an offline look up table. The look up table assigns an optimal schedule with associated optimal LQG controller to initial conditions. The proposed scheme improves previous results by online deployment of schedule and LQG control with stability guarantees and very low computational overhead. A simulation example with communication delays, packet losses and bandwidth limitations in both sensor and actuator sides is included. Static optimal periodic communication sequence, Optimal Pointer Placement (OPP) approach proposed in previous works, a random access scheduling method representing contention based access policies and the proposed method are simulated and compared.      

连续时间MCP在紧致行动集上的最优策略

文中研究了一类连续时间Markov控制过程(CTMCP)无穷水平平均代价性能的最优控制决策问题.文章采用无穷小生成元和性能势的基本性质,直接导出了平均代价模型在紧致行动集上的最优性方程及其解的存在性定理,提出了求解ε-最优平稳控制策略的数值迭代算法,并给出了这种算法的收敛性证明.最后通过分析一个数值例子来说明这种方法的应用.     

Online Optimization of Data Transmission Policies for Wireless Networks

In wireless communication networks, power control is necessary to maintain desired link quality, minimize interference and prolong battery lifetime of mobile terminals. In this technical note we describe the wireless channel of a wireless network as a finite state Markov chain and study packet transmission strategies for data services. Under the Markov channel assumption, we prove the optimal strategy is of threshold structure: corresponding to each channel state there exists a positive threshold on queue length; once the queue length exceeds the threshold, the network should transmit packets over its available capacity; otherwise there should be no transmission. A single sample path-based optimization algorithm is proposed to tune the thresholds. Since only a single sample path is involved, the proposed algorithm can be implemented online.      

变结构双模数字控制算法的研究与应用

针对钢板宽度测控系统数学模型的特点，提出了一种变结构双模控制方法。该方法将线性控制与非线性控制有机结合，实现了钢板宽度的测量与优化控制。实际运行结果表明该方法可靠、有效。     

Optimal Control of Queuing Systems with Channel Switching

Automation and Remote Control - We consider the problem of optimizing the operation of a queuing system in which the number of working service channels can be changed in a controlled manner at...     

跨区域通信信息传输性优化设计

近年来,随着我国经济的快速发展,民众对通信信息传输提出了更高的要求,这使跨区域通信信息传输成为电力通信领域在发展过程中迫切需要解决的重要问题之一。为了使跨区域通信信息传输具备更低的建设与维护成本,需要采用相应的优化设计方法来提高系统的可靠性。本文对跨区域通信信息传输性优化设计需要考虑的问题进行深入分析,明确了跨区域通信信息传输性优化设计在实施过程中需要遵循的相关原则,并在此基础上提出跨区域通信信息传输性优化设计的实现方案,以期能够推动我国电力通信领域的进一步发展。     

Properties of Combinatorial Optimization Problems Over Polyhedral-Spherical Sets

The class of combinatorial optimization problems over polyhedral-spherical sets is considered. The results of theory of convex extensions are generalized to certain classes of functions defined on sphere-located and vertex-located sets. The original problem is equivalently formulated as a mathematical programming problem with convex both objective function and functional constraints. A numerical illustration and possible applications of the results to solving combinatorial optimization problems are given.     

一种适用于WMSNs传输机制的信道盲估计方法

虚拟MIMO是一种克服无线多媒体传感器网络信道多径衰落和降低节点能耗的有效方法,但现有文献均假设信道状态信息未知或仅知道信道的统计特性,源节点则无法根据信道的实时信息动态调整传输策略。针对WMSNs信道特点,提出一种适用于WMSNs传输机制的信道盲估计方法以获得节点间信道信息进而确定传输策略,通过构造权值衰减联合决策函数,将节点间的信道盲估计问题转化为一个无约束优化问题,在此基础上设计了一种快速收敛的迭代算法以降低运算代价。该方法仅依赖小数据量就可正确估计出节点间信道,具有对抗信道时变特性的能力;理论推导与仿真表明该算法的收敛速度和运算量均能符合降低节点能耗的要求。